Polyurethane resins are produced by reacting a polyol and a polyisocyanate in the presence of a catalyst and as required by necessity, a blowing agent, a surfactant, a flame retardant, a cross-linking agent, and/or the like. The use of many metallic compounds and tertiary amine compounds as the catalyst in the manufacture of polyurethane resins is known. These catalysts are heavily used industrially either alone or in combination.
In the manufacture of polyurethane foam using water and/or a low-boiling point organic compound as the blowing agent, a tertiary amine compound is particularly widely used among these catalysts since it has excellent productivity and moldability. Examples of such a tertiary amine compound include conventionally well-known triethylenediamine, N,N,N′,N′-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl)ether, N,N,N′,N″,N″-pentamethyl diethylenetriamine, N-methyl morpholine, N-ethyl morpholine, N,N-dimethylethanolamine (for example, refer to Non-Patent Document 1). In most cases, metallic compounds are combined with tertiary amines and not used alone since productivity and moldability worsen.
The above-mentioned tertiary amine catalyst gradually discharges as a volatile amine from a polyurethane product and, for example, an odor problem is caused by the volatile amine in interior materials of vehicles and the like, and a discoloration problem of other materials such as vinyl chloride is caused. Also, generally tertiary amine catalysts have a strong odor and the work environment at the time of polyurethane resin manufacture becomes remarkably worse. As methods for solving the problems relating to these volatile tertiary amines, the use of amine catalysts which have at least one primary or secondary amino group or at least one hydroxyl group in the molecule that can react with a polyisocyanate (hereinafter may also referred to as reactive catalyst) and the use of a bifunctional cross-linking agent which includes a tertiary amino group in the molecule have been proposed (refer to Patent Documents 1-4).
It is said that the above-mentioned problems may be avoided by using the above-mentioned methods utilizing a reactive catalyst, since the reactive catalyst is fixed in the polyurethane resin backbone in the form of reacting with polyisocyanate. Although the methods may be effective in reducing the odor in the final resin product, these methods cannot be used as methods to improve the work environment at the time of polyurethane resin manufacture since these amine catalysts are volatile. Also, there is a problem that the physical properties of the polyurethane resin such as hardness are reduced.
Furthermore, although the above-mentioned method using a cross-linking agent is effective in reducing the odor in the final resin product and improving the work environment at the time of polyurethane resin manufacture, the physical properties of the polyurethane resin such as hardness are insufficient.
On the other hand, an alkylene oxide adduct of N,N-dimethyldipropylenetriamine and the like has been proposed as a trifunctional polyol including a tertiary amino group in its molecule (for example, refer to Patent Document 5). This polyol has three hydroxyl groups in its molecule and although there is potential that the above-mentioned problems can be solved, the cost of raw material compounds when preparing this polyol is expensive. Thus, there are problems such as high preparing costs when this is used in the manufacture of a polyurethane resin.
Also, many alkylene oxide adducts of ethylene diamine are commercially available in order to reduce the amount of the tertiary amine catalyst used (hereinafter may also referred to as amine polyols). Although these amine polyols only have a little unpleasant odor and are effective in improving the work environment since the amount of the tertiary amine catalyst used can be reduced, their catalytic activity is small and as a result, it is necessary to use a large quantity thereof. Thus, there are problems such as reduction in the flame retardancy of the rigid polyurethane foam.
On the other hand, although metallic catalysts do not cause the odor problem and the problem of degrading other materials like the tertiary amines, when a metallic catalyst is used alone, productivity, physical properties, and moldability worsen as described above and furthermore, the toxicity problem and environmental problems by the heavy metals which remain in the product have received attention. For example, although dibutyltin dilaurate or lead octanoate is used in the manufacture of a spray-type rigid polyurethane foam by which polyurethane foam is formed by being discharging in a mixture by a spray, a substitute for these is strongly desired.    Patent Document 1: Japanese Unexamined Patent Application, First Publication No. S46-4846    Patent Document 2: Japanese Examined Patent Application, Second Publication No. S61-31727    Patent Document 3: Japanese Patent No. 2971979    Patent Document 4: Japanese Unexamined Patent Application, First Publication No. S63-265909    Patent Document 5: Japanese Unexamined Patent Application, First Publication No. H5-214091    Non-Patent Document 1: Keiji Iwata “Polyurethane Resin Handbook”, page 118, (First Edition 1987) Nikkan Kogyou Shinbun, Ltd.